Non-cytotoxic urethane elastomer

Abstract

A non-cytotoxic polyether polyurethane elastomer is made by reacting a polyether triol, polyether diol, and polyether prepolymer terminated with toluene diisocyanate. The reaction is catalyzed with a zinc based catalyst, such as zinc neodecanoate. Silicone oil is also added to the reactants. The polyurethane elastomer is a solid, soft elastomer having a hardness of from 15 Shore 00 to 50 Shore A. The elastomer is particularly suited for use as padding in sleeves, splints and braces where it is in contact with human skin.

The invention claimed is: 
     
       1. A non-cytotoxic crosslinked soft polyurethane elastomer composition comprising the reaction product of:
 (a) at least one hydroxyl terminated polyether, wherein said polyether has a functionality of greater than 2, and wherein said polyether is a triol having a number average molecular weight of from 500 to 700 Daltons, said polyether triol being present at a level of from 5 to 12 weight percent, based on the total weight of said composition; 
 (b) at least one hydroxyl terminated polyether diol, wherein said diol has a number average molecular weight of from 4,000 to 12,000 Daltons; 
 (c) at least one polyether prepolymer terminated with a diisocyanate; and 
 (d) at least one zinc based catalyst suitable to react (a), (b) and (c) above to form a crosslinked soft polyurethane elastomer, wherein the zinc based catalyst is present at a level of from 0.25 to 0.6 weight percent of said composition; 
 wherein said crosslinked soft polyurethane elastomer composition has a hardness from 15 Shore 00 to 50 Shore A, as determined according to ASTM D2240. 
 
     
     
       2. The crosslinked soft polyurethane elastomer composition of  claim 1  further comprising from 0.3 weight percent to 1.5 weight percent of at least one silicone oil, based on the total weight of the composition. 
     
     
       3. The crosslinked soft polyurethane elastomer composition of  claim 1 , wherein the hydroxyl terminated polyether diol in (b) has a number average molecular weight of from 6,000 to 10,000 Daltons. 
     
     
       4. The crosslinked soft polyurethane elastomer composition of  claim 1 , wherein the diisocyanate in (c) is toluene diisocyanate. 
     
     
       5. The crosslinked soft polyurethane elastomer composition of  claim 4 , wherein the polyether prepolymer has less than 0.1 weight percent free toluene diisocyanate. 
     
     
       6. The crosslinked soft polyurethane elastomer composition of  claim 1 , wherein the hardness is from 20 Shore 00 to 20 Shore A. 
     
     
       7. The crosslinked soft polyurethane elastomer composition of  claim 1 , wherein the hardness is from 20 Shore 00 to 70 Shore 00. 
     
     
       8. The crosslinked soft polyurethane elastomer composition of  claim 3 , wherein the hydroxyl terminated polyether diol is present at a level of from 55 to 75 weight percent, based on the total weight of said composition. 
     
     
       9. The crosslinked soft polyurethane elastomer composition of  claim 5 , wherein the polyether prepolymer is present at a level of from 15 to 30 weight percent, based on the total weight of said composition. 
     
     
       10. A non-cytotoxic crosslinked soft polyurethane elastomer composition comprising the reaction product of:
 (a) from 7.0 to 8.5 weight percent of at least one hydroxyl terminated polyether triol, said triol having a number average molecular weight from 500 to 700 Daltons; 
 (b) from 65 to 70 weight percent of at least one hydroxyl terminated polyether diol, said diol having a number average molecular weight from 7,000 to 9,000 Daltons; 
 (c) from 20 to 25 weight percent of at least one polyether prepolymer terminated with toluene diisocyanate, wherein said prepolymer has less than 0.1 weight percent of free toluene diisocyanate; 
 (d) from 0.3 to 0.4 weight percent of zinc neodecanoate catalyst; 
 said weight percents based on 100 weight percent of the reactants (a)+(b)+(c)+(d); wherein said composition comprises from 0.6 to 0.9 weight percent of silicone oil; and wherein said crosslinked soft polyurethane elastomer composition has a Shore 00 hardness of from 2.0 to 70, as determined according to ASTM D 2240. 
 
     
     
       11. The composition of  claim 10  comprising:
 (a) from 7.5 to 8.0 weight percent of said triol; 
 (b) from 68 to 70 weight percent of said diol; 
 (c) from 22 to 23 weight percent of said prepolymer; 
 (d) from 0.3 to 0.4 weight percent of said zinc neodecanoate catalyst; and 
 (e) from 0.7 to 0.8 weight percent of said silicone oil. 
 
     
     
       12. A non-cytotoxic article made from the composition of  claim 1  and when in use has one surface in contact with human skin. 
     
     
       13. The non-cytotoxic article of  claim 12 , wherein said article is a molded article. 
     
     
       14. A non-cytotoxic article made from the composition of  claim 11 . 
     
     
       15. A process for producing a non-cytotoxic crosslinked soft polyurethane elastomer composition comprising:
 (a) adding at least one hydroxyl terminated polyether to a mixing vessel, wherein said polyether has a functionality of greater than 2 and a number average molecular weight of from 400 to 1,000 Daltons; 
 (b) heating said polyether in (a) to a temperature of from 100° C. to 120° C. while mixing under vacuum for 10 to 20 minutes; 
 (c) adding at least one hydroxyl terminated polyether diol to said mixing vessel containing the polyether (a), wherein said polyether diol has a number average molecular weight of from 4,000 to 12,000 Daltons; 
 (d) mixing the mixture of (a)+(c) for 3 to 10 minutes under vacuum; 
 (e) cooling the mixture of (a)+(c) to less than 40° C.; 
 (f) adding to said cooled mixture at least one zinc based catalyst and at least one silicone oil; 
 (g) mixing said mixture under vacuum for 20 to 40 minutes; 
 (h) adding to said mixture of (a), (c) and (f) at least one polyether prepolymer terminated with a diisocyanate; and 
 (i) heating said mixture of (a), (c), (f) and (h) to a temperature of from 70° C. to 110° C. for a time sufficient to crosslink the composition to form a polyurethane elastomer with a hardness of from 15 Shore 00 to 50 Shore A, as determined by ASTM D2240. 
 
     
     
       16. The process of  claim 15 , wherein the ingredients (a), (c) and (f) form the first part of a two part system, and ingredient (h) forms the second part of the two part system. 
     
     
       17. The process of  claim 16 , wherein each of the first part and second part are packaged separately under nitrogen for use at a later time. 
     
     
       18. The process of  claim 16 , wherein for every 100 parts by weight of the first part of the mixture, from 25 to 35 parts by weight of the second part is mixed with the first part. 
     
     
       19. The process of  claim 18 , wherein the hydroxyl terminated polyether with a functionality of greater than 2 in claim  15 (a) is a triol. 
     
     
       20. The process of  claim 19 , wherein the polyether prepolymer in claim  15 (h) is terminated with toluene diisocyanate, and wherein said prepolymer has less than 0.1 weight percent free toluene diisocyanate. 
     
     
       21. The process of  claim 15 , wherein the mixture in (i) is heated to a temperature of from 78° C. to 82° C. for a time of from 14 to 18 hours to form a polyurethane elastomer having a hardness of from 20 to 50 Shore 00. 
     
     
       22. The process of  claim 18 , wherein after the mixing of the first part with the second part, the mixture is poured into a mold within 1 hour after being mixed. 
     
     
       23. The process of  claim 15  comprising:
 (a) from 7.5 to 8.0 weight percent of said at least one hydroxyl terminated polyether having a functionality of greater than 2, and wherein said hydroxyl terminated polyether is a triol; 
 (b) from 68 to 70 weight percent of said diol; 
 (c) from 22 to 23 weight percent of said prepolymer; 
 (d) from 0.3 to 0.4 weight percent of zinc neodecanoate catalyst; and 
 (e) from 0.7 to 0.8 weight percent of said silicone oil.